diff options
Diffstat (limited to 'tools/tracing/rtla/src/timerlat_u.c')
| -rw-r--r-- | tools/tracing/rtla/src/timerlat_u.c | 224 |
1 files changed, 224 insertions, 0 deletions
diff --git a/tools/tracing/rtla/src/timerlat_u.c b/tools/tracing/rtla/src/timerlat_u.c new file mode 100644 index 000000000000..05e310696dd5 --- /dev/null +++ b/tools/tracing/rtla/src/timerlat_u.c @@ -0,0 +1,224 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2023 Red Hat Inc, Daniel Bristot de Oliveira <bristot@kernel.org> + */ + +#define _GNU_SOURCE +#include <sched.h> +#include <fcntl.h> +#include <stdlib.h> +#include <unistd.h> +#include <stdio.h> +#include <errno.h> +#include <string.h> +#include <tracefs.h> +#include <pthread.h> +#include <sys/wait.h> +#include <sys/prctl.h> + +#include "utils.h" +#include "timerlat_u.h" + +/* + * This is the user-space main for the tool timerlatu/ threads. + * + * It is as simple as this: + * - set affinity + * - set priority + * - open tracer fd + * - spin + * - close + */ +static int timerlat_u_main(int cpu, struct timerlat_u_params *params) +{ + struct sched_param sp = { .sched_priority = 95 }; + char buffer[1024]; + int timerlat_fd; + cpu_set_t set; + int retval; + + /* + * This all is only setting up the tool. + */ + CPU_ZERO(&set); + CPU_SET(cpu, &set); + + retval = sched_setaffinity(gettid(), sizeof(set), &set); + if (retval == -1) { + err_msg("Error setting user thread affinity\n"); + exit(1); + } + + if (!params->sched_param) { + retval = sched_setscheduler(0, SCHED_FIFO, &sp); + if (retval < 0) { + err_msg("Error setting timerlat u default priority: %s\n", strerror(errno)); + exit(1); + } + } else { + retval = __set_sched_attr(getpid(), params->sched_param); + if (retval) { + /* __set_sched_attr prints an error message, so */ + exit(0); + } + } + + if (params->cgroup_name) { + retval = set_pid_cgroup(gettid(), params->cgroup_name); + if (!retval) { + err_msg("Error setting timerlat u cgroup pid\n"); + pthread_exit(&retval); + } + } + + /* + * This is the tool's loop. If you want to use as base for your own tool... + * go ahead. + */ + snprintf(buffer, sizeof(buffer), "osnoise/per_cpu/cpu%d/timerlat_fd", cpu); + + timerlat_fd = tracefs_instance_file_open(NULL, buffer, O_RDONLY); + if (timerlat_fd < 0) { + err_msg("Error opening %s:%s\n", buffer, strerror(errno)); + exit(1); + } + + debug_msg("User-space timerlat pid %d on cpu %d\n", gettid(), cpu); + + /* add should continue with a signal handler */ + while (true) { + retval = read(timerlat_fd, buffer, 1024); + if (retval < 0) + break; + } + + close(timerlat_fd); + + debug_msg("Leaving timerlat pid %d on cpu %d\n", gettid(), cpu); + exit(0); +} + +/* + * timerlat_u_send_kill - send a kill signal for all processes + * + * Return the number of processes that received the kill. + */ +static int timerlat_u_send_kill(pid_t *procs, int nr_cpus) +{ + int killed = 0; + int i, retval; + + for (i = 0; i < nr_cpus; i++) { + if (!procs[i]) + continue; + retval = kill(procs[i], SIGKILL); + if (!retval) + killed++; + else + err_msg("Error killing child process %d\n", procs[i]); + } + + return killed; +} + +/** + * timerlat_u_dispatcher - dispatch one timerlatu/ process per monitored CPU + * + * This is a thread main that will fork one new process for each monitored + * CPU. It will wait for: + * + * - rtla to tell to kill the child processes + * - some child process to die, and the cleanup all the processes + * + * whichever comes first. + * + */ +void *timerlat_u_dispatcher(void *data) +{ + int nr_cpus = sysconf(_SC_NPROCESSORS_CONF); + struct timerlat_u_params *params = data; + char proc_name[128]; + int procs_count = 0; + int retval = 1; + pid_t *procs; + int wstatus; + pid_t pid; + int i; + + debug_msg("Dispatching timerlat u procs\n"); + + procs = calloc(nr_cpus, sizeof(pid_t)); + if (!procs) + pthread_exit(&retval); + + for (i = 0; i < nr_cpus; i++) { + if (params->set && !CPU_ISSET(i, params->set)) + continue; + + pid = fork(); + + /* child */ + if (!pid) { + + /* + * rename the process + */ + snprintf(proc_name, sizeof(proc_name), "timerlatu/%d", i); + pthread_setname_np(pthread_self(), proc_name); + prctl(PR_SET_NAME, (unsigned long)proc_name, 0, 0, 0); + + timerlat_u_main(i, params); + /* timerlat_u_main should exit()! Anyways... */ + pthread_exit(&retval); + } + + /* parent */ + if (pid == -1) { + timerlat_u_send_kill(procs, nr_cpus); + debug_msg("Failed to create child processes"); + pthread_exit(&retval); + } + + procs_count++; + procs[i] = pid; + } + + while (params->should_run) { + /* check if processes died */ + pid = waitpid(-1, &wstatus, WNOHANG); + if (pid != 0) { + for (i = 0; i < nr_cpus; i++) { + if (procs[i] == pid) { + procs[i] = 0; + procs_count--; + } + } + break; + } + + sleep(1); + } + + timerlat_u_send_kill(procs, nr_cpus); + + while (procs_count) { + pid = waitpid(-1, &wstatus, 0); + if (pid == -1) { + err_msg("Failed to monitor child processes"); + pthread_exit(&retval); + } + for (i = 0; i < nr_cpus; i++) { + if (procs[i] == pid) { + procs[i] = 0; + procs_count--; + } + } + } + + params->stopped_running = 1; + + free(procs); + retval = 0; + pthread_exit(&retval); + +} |